Identification and biocontrol of the key pathogenic fungus inhibiting tuber expansion in Rehmannia glutinosa from Henan Province

Rehmannia glutinosa (R. glutinosa) is a characteristic medicinal crop indigenous to Henan Province, China. The suppression of tuber expansion caused by continuous cropping obstacles (CCOs) remains a persistent challenge in R. glutinosa cultivation. Studies have revealed that CCOs increase the abundance of pathogenic fungi in rhizosphere soil. However, the key pathogenic fungus responsible for CCOs induced tuber growth inhibition in Henan Province remains unidentified. In this study, the key pathogenic fungus was isolated and identified by combining plate co-culture, pot experiments and metagenomic analysis. Further, the antagonistic strain targeting the key pathogenic fungus was obtained using biocontrol strategy. The result indicated that Fusarium oxysporum DC7 (F. oxysporum DC7) could be identified as the key pathogenic fungus. F. oxysporum DC7 significantly inhibited the fresh weight and dry weight of R. glutinosa tubers by 75.64% and 88.97%. Metagenomics analysis revealed that the relative abundance of F. oxysporum obviously enriched in consecutively monoculture rhizosphere soil, which was consistent with the trend of the severity of CCOs. Aspergillus terreus FL13 (A. terreus FL13) was further identified as the antagonistic strain against F. oxysporum DC7. Biocontrol experiments confirmed that A. terreus FL13 effectively alleviated the inhibitory effect induced by F. oxysporum DC7. In addition, F. oxysporum DC7 caused detrimental alterations to the soil microenvironment, leading to significant reductions in total phosphorus and organic matter. A. terreus FL13 exhibited the capacity to restore the compromised soil microenvironment. In conclusion, this study identified the key pathogenic fungus responsible for inhibiting tubers expansion in R. glutinosa cultivated in Henan Province and established an effective biocontrol strategy to mitigate this agricultural challenge.